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International Conferences on Recent Advances 1995 - Third International Conference on Recent in Geotechnical Earthquake Engineering and Advances in Geotechnical Earthquake Soil Dynamics Engineering & Soil Dynamics
07 Apr 1995, 10:30 am - 11:30 am
Review of Geotechnical Investigations Resulting from the Roermond April 13, 1992 Earthquake
P. M. Maurenbrecher TU Delft, The Netherlands
A. Den Outer TU Delft, The Netherlands
H. J. Luger Delft Geotechnics, The Netherlands
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Recommended Citation Maurenbrecher, P. M.; Den Outer, A.; and Luger, H. J., "Review of Geotechnical Investigations Resulting from the Roermond April 13, 1992 Earthquake" (1995). International Conferences on Recent Advances in Geotechnical Earthquake Engineering and Soil Dynamics. 5. https://scholarsmine.mst.edu/icrageesd/03icrageesd/session09/5
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Review of Geotechnical Investigations Resulting from the Roermond April 13, 1992 Earthquake Paper No. 9.16
P.M. Maurenbrecher and A. Den Outer H.J. Luger Lecturer and Ph.D. Researcher, TU Delft, The Netherlands Project Engineer Delft Geotechnics, The Netherlands
SYNOPSIS In 1987 the Engineering Geology section of the Delft University of Technology carried out a survey of the SE Netherlands to determine which areas were susceptible to liquefaction based on soil profile, groundwater levels and a Richter scale magnitude 6 earthquake along the prin.::ipal rift fault through the Netherlands, the Peelrand fault system. The fault system has been active since the Triassic and forms part of the Rhine-North Sea rift system. The last major ear~hquake along the Peelrand fault was in 1933. Recently, in 1992. a 5.8 magnitude earthquake occurred at Roermond, near to the Dutch-German border. Though damage resulting from the earthquake was limited, remedial works to structures amounted to US$ 50 million in the Netherlands. The paper reviews geotechnical investigations associated with the earthquake carried out in the Netherlands. Much of the damage is attributed to liquefaction; excess pore pressures resulting from the earthquake caused sand vent eruptions, river-dyke failures and slope failures. Comparisons are made between the predictions of 1987 and that which occurred in 1992.. Site investigation works are recording geotechnical and building data so as to allow for correlations between extent of damage, ground geotechnical profiles and building design. Models for liquefaction are reviewed to describe the slope failure as well as the sand vent phenomena. Densification of subsoil has been inferred from CPTs taken before and after the earthquake for some sites. Pile foundation damage has been investigated for buildings in Roermond for which their susceptibility to earthquake lateral forces in terms of stiffness and pile head working loaJ is given.
INTRODUCTION Earthquake hut 60 km to the northwest. These earthquakes have been estimated to have a recurrence period of 12.0 to 140 At 03:30 hrs early Monday morning of the 13th Aprill992. an years. Research into earthquakes is not new in to the earthquake of magnitude 5. 8 on the Richter scale occurred in Netherlands. The number of researchers in this field is though the southeastern part of the Netherlands near the border with very limited; the seismological office of the Royal Germany. The earthquake is the strongest ever recorded in the Meteorological Institute in de Bilt and a number of researchers Netherlands and caused damage amounting to $50 million. at the University of Utrecht Geological Institute and at the Only one death, due to heart failure, has been attributed to Delft University of Technology Engineering Geology Section. earthquake, in Germany. The low human injuries resulted Research at Delft had been active in this field a number of from the earthquake happening during the most quiet period of years investigating the susceptibility of "foundation zone" the week; early Monday morning when even the night life in deposits to liquefaction in the southeastern part of the the Netherlands is at its lowest. No occurrence of building Netherlands assuming an earthquake epicentre along the collapse has been recorded which may be the other factor Peelrand fault of magnitude 6 on the Richter scale. The limiting human injuries. Buildings, though, were damaged. location map in Fig. 1 shows the susceptible areas (Lap 1987) The damage required, in most cases, repairs to cracks, though and the significant geographical locations with respect to the buildings in Herkenbosch, Roermond and Heinsherg and Roermond Earthquake. villages nearby damage to many building consisted of some form of collapse: chimneys, gables, ceilings and roof tiles. Had the earthquake occurred during lunch time on what was POST EARTHQUAKE INVESTIGATION otherwise a relatively sunny spring day many pedestrians may have fallen victim to the falling debris. The Roermond Earthquake has motivated further research activity to both attempt to record and relate damage of Earthquake phenomena is not new to the Netherlands, though buildings as a result of the response of these buildings and the the scale and timing of the Roermond Earthquake was ground they are founded on to the various forces generated by unexpected. The last major earthquake was that of Uden in the earthquake. In addition ground disturbances attributed to 1933 (5.5 on the Richter scale), the epicentre on the same liquefaction manifested itself as sand eruptions, slope failures Peelrand fault-line system as that for the Roermond and embankment collapse. A symposium was held nine months
645 after the earthquake to allow presentation and discussion of with researches in the Roermond Earthquake. initial studies and initiatives on the earthquake. The proceedings on the symposium will be published shortly, (van Geotechnical work on the Roermond earthquake in the Eck, 1994). Various groups were formed such as the Netherlands has been limited to a few investigators within two seismological, information and geotechnical to ensure Delft institutes: Delft Geotechnics which has carried out subsequent to the symposium contact between the researchers investigations on behest of the municipality of Roermond and is maintained. The geotechnical and information groups are the Engineering Geology Section of the Technical University sustained by TU Delft Engineering Geology Section. Activity Delft as a continuation of earlier research and within on the information group has recently been reported at the university funded engineering geology mapping project for the Geolnfo V conference held in Prague in June 1994 (den Outer province of Limburg (south east Netherlands) in which the et al., 1994) in which present information storage and earthquake occurred. anticipated development are outlined. The work from Delft Geotechnics investigated possible unseen The geotechnical group activity subsequent to the symposium damage to foundations of houses both on shallow and on piled has been limited to compiling and submitting research foundations. The area that was particularly of concern by the proposals in cooperation with many institutes in Germany, the municipality of Roermond is along an old tributary of the Netherlands, Belgium and England for European Commission River Roer to the east of the city and corresponds to the high finance. Though unsuccessful the initiatives maintain contact liquefaction potential (shaded) area shown in Fig. 1 .
51°30' 390
380
370 ~ 360 ~ 350 ~
340
330 unlikely to occur
::;:: ::::;.:::::;:::] areas with a low ;::: ; :>>:::: >:::j liquefaction potential 320 1 areas with a medium liquefaction potential 310 areas with a high liquefaction potential 300 120 140 160 180 200 220 240 Fig. 1. Liquefaction potential map of southeast Netherlands for Richter Scale magnitude 6.0 along the Peelrand Fault (Lap, 1987).
646 o 5 10 15 20 2li 30 o 0.2 o.4 o.& o.a 1.2 1.• The work from the TU Delft Engineering Geology Section as I 22 +-'-.-+-+--+.-+-+---'' a consequence of the earthquake investigated two locations: the \ 1: t'· t I ~ :\;::.I, relatively heavily damaged town of Herkenbosch, sand I I . ':- -:- I 1; FOUNDATION SUSCEPTIBILITY TO DYNAMIC LOADS I I I I I II The most common application of the cone penetration test 0.02 0.05 0.1 0.2 0.5 , 2 5 10 20 (CPT) is to determine the soil profile and its load bearing r ~: ;;\ co vol lower scale properties for a foundation. The point resistance together with C:.::::. q c(MPa) ;-_.:::=, Az mm top scala the friction resistance allows an accurate determination of the -··-· Yground (kN/m3) 1 -'- (• / fJ ) 10 lC top acal,. soil type'. In the Netherlands this is generally done for every - IP (%) 10x scale c v &vii pile location below a foundation to find the end-bearing layer -- G 1 (MPa) 10 x scalot --am&>< m/s 2 top scale of the pile. It is this standard procedure that allows for estimating foundation susceptibility to dynamic loading [Luger Fig. 2. Soil profile data and calculated values et al., to be published; Meijers eta!., to be published]. In the city of Roermond (the Maasniel district) CPT analysis, causing a CPT resistance of 30 MPa. The upper part of the verified witi1 borings, shows a 6 to 12 m thick layer of loose/ weak layers has been further disturbed by clay varying soil types, eg. predominantly fluvial deposits of low exploitation for brick making. The pits have been generally density or strength varying in grain size from sands to silty infilled with building debris and refuse. clays. Below these deposits further over-consolidated fluvial deposits consisting of dense sands and gravels are encountered Fig. 2 shows the various profiles of the CPT end bearing, qc, 3 0.8 0.6 2 1<"" (J) 0.4 1<"" Cll §,-- 0.2 ~ tU Ill c 0 c 1/ ~ 0 0 "Q 0.8 ----- ~... ~.2 "'lii Q) 0.6 ~.4 I/ - § ~ 0.5 tU Ill ~.6 0.4 1/ -0.8 -1 0.5 2 3 5 10 20 30 0 2 10 frequency (Hz) time (seconds) Fig. 3. Ground acceleration response spectrum (Hosser 1987) Fig. 4. Generated acceleration record 1[In fact several researchers have determined such correlations (Schmertmann, 1977, Searle, 1979 and Olsen & Malone, 1988). Searle's chart, the most ambitious of the three, allows, just about, every soil parameter to be derived from the point resistance/ friction ratio relation and is shown as part of fig. 6. The more recent chart from Olsen and Malone allows a more limited selection of more descriptive soil parameters, allowance is made for insitu stresses, and hence can be considered the more 647 and the interpreted soil parameter values: in-situ relative density (I 0 ) and the dynamic shear modulus (G) of the layers. 10 ~ max bending moment kNm ~~ These values are obtained from a knowledge of qc and the • Max pile head aoceleraflon 0.1 mts• types of soil from borehole logs using correlation.s based on 70 ll Moment of 1st yil'k! KNm I>c ~ /:! Lunne et a!., 1983 and Richart et a!. , 1970. In th1s way the c :! ~~ 60 ! .6 § relevant parameters are obtained to allow estimates to be ma~e "! "! B .6B ..... Ill Ill II~ oo...... of densification and the strain of each layer under dynam1c ~ liO a a i I loading. :::E :::E5 ::1! :::E :::E oil .0 ... ~• "" "" ""~• • ~ The program SHAKE (Schnabel et a!. 1972) is used to predict (!) (!I (!) 30 !ia i i !ia che ground motion due to dynamic loading. In addition t? t.he w w geotechnical profiles the program requires some charact~nst1cs 20 of the signature of the earthquake. The length of penod of strong motion has been estimated from the e~rthquake 10 x required eooentrtdty an magnitude at 10 seconds, with a maximum acceleratiOn of?· 9 ,, max lateral load 0.01MN 2 m/s • For the area under investigation the ground acceleratiOn 0 +------.,------,--,---,---,----·~---.-----' 0.5 1.5 2.5 3.5 •.s response spectrum, with predominant frequencies ~Jetween 3 and 5Hz, was obtained from Hosser,(l987), see f1g. 3. The Correlation trend factor 0.01 v'E x Pile head mass inverse Fourier transform of this response spectrum, adapted for 5% damping and random phase behaviour in the time Fig. 5. Pile calculated values domain, will give the earthquake signature that is needed for the program SHAKE. dynamic energy is small and of a specific energy content Using the output of the program SHAKE (displacement and (mass of falling driving weight). The discontinuous character stresses of the subsoil) the shear strain and therefore the of the test is a real disadvantage while the transitions of the volumetric strain (see soil response in fig 2) is obtained, which individual layers might lie within one SPT-N value result is an estimate for the settlement of the layers (5mm). It determination. was found that there is no excessive settlement expected at the considered location, however, differential settlement between 1 Th. ere "~r" - ··,~,;,) ··· ,.. ~VU ,-' co1·rdations of the CPT values wilh the back-filled pits and their surroundings should be watched. for. 0 SPT-N values (Burland et a!., 1985) and the continuous The maximum ground acceleration might have been h1gher 2 character of the CPT test is an advantage over the SPT -N. than 0.9 m/s , which can give problems for soils with a lower relative density than 40%. Recent research (Mwingira, 1994) has shown that the CPT can be converted well for the standard CPT-cone of 60° depending The resulting calculated data from SHAKE was input into a on the D of the soil grain size. Additionally a small programme TILLY (DUT 1992) for estimating lateral pi.le 50 correction for the overburden stress has to be done to make displacement and soil reaction force based on P~ Y analyses m the conversion complete. accordance with API (1989 edition). The key mput data and main results of the analyses are given in fig. 5. for a bored After obtaining the SPT-N values from the CPT test the SPT pile 11 m long and 0. 3 m diameter and having a de-sign !~ad N values for the Tsuchida method or the relative density for of 30 :MN. The effect of eccentric loading causes a reductiOn the Seed and Idris method can be fully implemented to get the of the maximum allowable bending moment. The calculation final estimate of the liquefaction susceptibility. The kinematic show that the lateral loading bending moment exceed those of processes and geotechnical profile are shown in fig. 6 from wind loading by a factor of two. There is a possibility that (Maurenbrecher et al 1994). critical overloading could have occurred. Further investigation, in the field, is required to verify any damage. Using the cone end bearing values, qc of the CPT the soil profile values are determined for input into the susceptibili~y SLOPE STABILITY AND SUSCEPTIBILITY TO analysis based on that of Seed et a!. ( 1983). The analysis DYNAMIC LOADS showed that the slope needed only very small acceleration of 0.06g to become unstable. This would correspond to the likely A very important use of the relative density obtained from tl:e acceleration from the earthquake. Brunssum was not classified CPT test is the determination of possible liquefying layers 1n by Lap (1988) as an area susceptible to liquefaction (see fig the subsoil. The methods often used to obtain susceptibility to 1). The area has been prone to liquefaction slides due to high liquefaction are Tsuchida ( or more popular Seed and Idris. pore water pressure in a loose sand spoil derived from lignite Both methods use the SPT-N value to express the influence of mining. Further more the area is the source of the Roodebeek the relative density on the process of liquefaction. The stream with the springs and associated quicksands within the dynamic character of the SPT-N is seen as .an advantage to vicinity of the failed slopes. express the dynamic behaviour of the subsoiL However, the 648 ...... 1 . 0 0 ~~~----~~~~ water level.. E t2 CPT2 . •c! ...... 1 . metre 0 05 15 " t qe t.4Pa 5 em2 CPT-oone & blow8/2mm OPT · : 0········· ~0.5 1.5 ...... q~ · t.4Pa" 5 em 2 cone· .. 0 0.5 , 1.1 0 o.s . , qe MPa 5 cmz cone q MPa 10cm2 cone lo ' I I ' o.i i 0 ...... q .. MPa·.. 10 em 2 cone -...... t O' ...... i ....l. 03 ...... •... • ... ! .. 1 0 q c MPa 10 cm2 cone Fig. 6. Brunssum slope liquefaction kinematics & geotechnical profile HERKENBOSCH SAND-WATER VENTS Substantial water-sand outflow occurred from linear fissures in the ploughed fields between the town of Herkenbosch and the Rive Roer. Excavation revealed cracks infilled with sand extending to a sand source layer two to three metres underneath the top layer consisting of slightly clayey silt (fig. Ba.nd til 7). The latter is quite impervious as the excavations were vorm hol relatively dry despite a preceding very wet autumn period. Davenport et al. (1994) attribute the fissures to follow a brittle type failure and have the same pattern a.<; subjecting a cake of clay to tension and are characteristic of surface strains Liqueta.ction associated with flow-type failure at depth. At least two metres det>Qait of excess pore water pressure was required to cause the water Gravel to reach the surface for a piezometric head estimated at two meter below ground level. This is probably caused by Fig. 7. Composite block diagram of liquefaction structures, densification of the sand and sandy gravel layers beneath ( see Herken bosch 649 fig 8) resulting in a volume decrease forcing water to escape. lying flood plane levels. Densification is suggested by CPTs The fissuring process providing escape routes for the water are at a location in Herkenbosch taken before and after the believed to result from horizontal displacements of the higher earthquake (fig 9). This however must be checked and verified Roer river flood plane terraces moving towards the lower by other tests carried out with a large time span between the a.q 00 0 350.5 ('I Qc MPa(~ ) 0 15 20 25 0 5 1 0 15 0 5 1 0 15 20 28 ...... , ..BH.1...... 2 2 ...... BH2 Ill t ~ ~ ..... 4 .. E. .s::. ..Q:6 ...... - ...... CD ~ Q. · ·· ··· · j· St ·· · · MPa· · (' · · ~.;;:::;/ ··t···· · ) · · · · ·· · · · ····· · ·· · · · · · · · t· · ·· ·· · ·· · · · ·· ·· ·· · · · ··· ·· · · · · · · · · · · ·· - · ' f I I I 0 .... 8 0 0.25 0 0 0.25 0 0.25 0.5 CLAY.·-· ~ - ~~ . +. ·. ~ .·.·. · .· .~ . · SAND SILT GRAVEL Fig. 8. Hetkenbosch: Soil profiles and ground fissuring extent at Herkenbosch 650 Cone. Resistance MPa qc 10 20 so 40 6 63 40 25 16 oP 10 6.3 Rf values CI'T 1 su.pe:r1111P0sed on qc;: v ll.f Chart ~--~~----~--~~--~--~---r---r--,---~~ 11 ~------J o.:zs 0 . 63 1.6 Friction Ratio R f {\) 1977 & 1992 Average CPT PROFILES Fig. 9. CPT profiles location A (fig. 7) before & after earthquake tests (25 years) without an earthquake evelit to determine other earthquakes are a continual hazard as unusual. Despite this, possible causes of densification such as the history of effective 'tremors do occur regularly in the vicinity of the Roer River stress fluctuations due to foundation loading and ground water graben (tectonic) and also due to extraction of hydrocarbons level changes. elsewhere in the Netherlands. Hence the need, despite relatively high quality construction, exists to be able to Through a questionnaire damage survey and the compilation determine the potential damage that earthquakes can induce on of geotechnical maps a better understanding of the relationship structures, not only for insurance accessors but also for safety between soil profile/ foundation and structure behaviour is reasons. The largest obstacle to research is finance. Injuries intended for the town of Herkenbosch (Outer and and loss of life often spur contributions. The Roermond Maurenbrecher, 1994) and (de Vries, 1994). Earthquake, despite being a 1 in 130 year event (Crouzen, 1993), seemed to choose a time of the day when such injury would be kept at a mini mum . Only si.x months later a FURTHER RESEARCH comparable earthquake both in g~ote chnica l environment and strength occurred in Cairo causing 200 d~ths. The timing was The Netherlands counts few researchers in the field of in the afternoon and the probably inferior structural integrity earthquake geotechnics as major earthquake events seldom of the buildings caused the higher loss of life. A great occur. Hence the approach to analyzing the geotechnical advantage over Egypt is the lesser damage to buildings does consequences of such an earthquake may seem to full-time not obscure as much the initial weakness of buildings and as earthquake geotechnical researchers from countries where there was no loss of life so that information from residents is 651 more complete. Furthermore site investigation frequency for of the Centre for Engineering geology in The Netherlands, buildings and contamination studies are done relatively TU Delft, No. 47, Vols 1 & 2, 40pp frequently with generally accessible archives of the information allowing detailed studies of soil profile Luger, H.J., Meijers, P. and Brinkman, J. to be published distribution. Such arguments seem to be lost on funding 1994, Loading of foundation piles during the Roermond organisations such as the European Union research Earthquake, Geologie and Mijnbouw, Kluwer. Geologie and programmes, which are more likely to provide funds to more Mijnbouw, Kluwer. vulnerable areas which in the longer term will not necessarily produce the right solutions. Lunne, T. & Christoffersen 1983, Interpretation of cone penetrometer data for offshore sands Offshore Technology Conf. Houston, 1983: 181-192 REFERENCES Maurenbrecher, P.M., Price, D.G. & Verwaal, W. to be Anon 1 1992, TILLY- User's Manual Version 3.1, Faculty published 1994, Brunssummerheide landslide Geologie and of Civil Engng. Jan. 1992 Delft University of technology Mijnbouw, Kluwer. Anon 2 1989, API 1989 Recommended Practice for Planning, Meijers, P., Luger, H.J. and de Lange, G. to be published Designing and Constructing Fixed Offshore Platforms RP 1994, Intluence of the Roermond earthquake on shallow 2A 18th Edition, Sept. 1989, American Petroleum Institute, foundations Geologie and Mijnhouw, Kluwer. Washington DC Mwingira, E.D.G. 1994, Liquefaction land slide in the Burland, J.B. & Burbridge, M.C. 1985, Settlement of Brunssummerheide, Brunssum MSc Thesis Int. lnst. for foundation on sand and gravel, Proc. Inst. Civil Engineers Aerospace Survey & Earth Sciences, lTC, Delft, Vol 1 and DEC. 1985 78 (Part 1), 1325-1381 2 Crouzen, L. 1993, Zuid-Nederland offici eel risicogehied Olsen, R.S. and Malone, P.G. 1988, Soil classification and aardbeving De Limburger 23 januari 1993 site characterization using cone penetration test" in Penetration Testing ISOPT-1, de Ruiter, J. (Ed) Vol 2 p888 Davenport, C.A., Lap, J.M.J., Maurenbrecher, P.M. & Price, D.G. to be puhlished 1994, Li,juefadiun potentiai l 6S2